The present invention relates to method and apparatus for producing a metal evaporated article.
In the production of a metal evaporated article, it is practiced to deposit an auxiliary material, such as margin forming oil, corrosion preventive oil or surface modifying material, by evaporation at predetermined portions on the surface of a substrate itself or the surface of a metal deposited on the substrate before or after metallizing the substrate.
The present invention particularly relates to method and apparatus for producing a metal evaporated article improved in the vapor deposition of an auxiliary material.
As a typical metallized film with a desired metal deposited on the surface of a film (substrate) made of a synthetic resin, etc., a metallized film for a capacitor is known. It is generally produced by a vacuum metallizer.
In this case, to form portions (margins) where any metal is not deposited on the substrate, it is practiced to deposit an oil by evaporation at the predetermined portions on the surface of the substrate before metallization.
Japanese Patent Publication (Tokko) 8-26449 discloses a method for forming margins by depositing a narrow thin oil layer by evaporation on the surface of a raw film for production of a metallized film for a capacitor.
Japanese Patent Laid-Open (Kokai) No. 59-227115 and Japanese Patent Publication (Tokko) No. 63-15735 propose methods for depositing an oil by evaporation on the surface of a metal layer formed on the surface of a substrate for preventing the corrosion of the metallized film.
These methods are excellent for the purpose of forming margins or forming a corrosion preventive layer.
A case of forming margins will be described hereunder. Since, generally, an oil using for it has dispersed molecular weight, it is intended to use an oil having narrow molecular weight distribution.
However, even if an expensive oil having narrow molecular weight distribution is used, the oil is somewhat different in molecular weight distribution between production lots. So, if an oil produced in a plurality of lots is used to form margins, it may happen that the formed margins become different in the state.
The reason is that where the oils are different in molecular weight distribution, the vapor pressures of the oils are different, and that even where the oil temperature is set at the same degree in respective evaporation batches, the quantity of the oil evaporated becomes different.
Furthermore, where an oil irregular in molecular oil distribution is kept evaporated at a predetermined oil temperature for a certain period of time, the oil components lower in molecular weight are evaporated at first, and it happens that the components evaporated at a predetermined temperature decrease remarkably even though there still remains much oil in the evaporator.
To avoid this problem, that is, to continuously form a thin oil layer with a certain thickness, it is necessary to always give a constant quantity of evaporated oil to the surface of the substrate.
To solve this problem, the operator gradually raises the oil temperature after depositing every thousands of meters, to keep the quantity of evaporated oil as constant as possible.
However, this temperature control relies on sensibility of the operator acquired on his or her experience for many years, and in addition, it cannot be confirmed during vapor deposition how much oil has been evaporated and how much oil has been deposited on the film by raising the temperature of oil. So, it is difficult to continuously keep the optimum quantity of oil over a batch film metallization length of tens of thousands of meters. As a result, in one metallization batch, the oil layer thickness varies and the margin formation also varies.
Furthermore, since the oil temperature must be raised manually frequently, operation errors are likely to be committed in margin formation.
Moreover, to form an oil layer with an optimum thickness on the film, the quantity of evaporated oil must be changed in response to the change of the running speed of the film to be treated, but the operator cannot respond to the change, and only raises the temperature of the oil constantly in evaporation operation even if the film speed varies.
If the quantity of oil in the thin oil layer deviates from the optimum value and becomes too small for the above reasons, the metal remains in the margin portions in the final product, to cause a metallization loss.
For the same reasons, also the prevention of corrosion of the deposited metal becomes functionally insufficient. On the other hand, if the quantity is too large, when the metallized film is used to form a capacitor element, press workability declines, to degrade the adhesion between films in the obtained capacitor. If a voltage is applied to the capacitor, the capacitor beats inconveniently.
Even when the auxiliary material is an organic compound or water, the deposited layer thickness cannot be measured during vapor deposition, and so it is difficult to deposit the layer continuously with the optimum thickness.
The object of the present invention is to overcome the above conventional problems by providing a process and apparatus for producing a metal evaporated article, which allow the stable formation of a layer of a deposited auxiliary material on a substrate.
The process and apparatus for producing a metal evaporated article of the present invention to achieve the above object are as follows.
A method for producing a metal evaporated article, which includes a metallization step of evaporating a metal and depositing the evaporated metal onto a continuously running substrate and an auxiliary material deposition step of evaporating an auxiliary material contained in an evaporator and depositing the evaporated auxiliary material onto the continuously running substrate, before or after the metallization step, comprising the steps of detecting the pressure of the atmosphere where the auxiliary material evaporated from the evaporator exists, and controlling the evaporation condition of the auxiliary material in the evaporator based on the information concerning the detected pressure.
In the method, the form of the substrate may be generally a continuous long sheet or film, or may also be short sheets or films, etc. having a predetermined length.
The material of the substrate is generally a natural, semi-synthetic or synthetic resin. Preferable synthetic resins which can be used here include polyolefin resins, polyester resins, polyimide resins, polyamidimide resins, polycarbonate resins, polysulfone resins, polyphenylene resins, polyallylate resins, fluorine resin and polystyrene resin.
When the metal evaporated article is a metallized film for a capacitor, the synthetic resins which can be preferably used in view of mechanical properties and electric properties include polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyphenylene naphthalate, polyphenylene sulfide, polycarbonate and polystyrene resin. Above all, polypropylene and polyethylene terephthalate resins can be especially preferably used since they are high in AC withstand voltage.
Conductive metals which can be deposited by evaporation include Al, Zn, Cu, Ag, Au, Sn, Ti, Co, Ni and their alloys. When the metal evaporated article is a metallized film for a capacitor, the conductive materials which can be preferably used among them in view of corona deterioration resistance are Al, Zn, Cu, Sn and their alloys. Among them, Alxe2x80x94Zn alloy is more preferable in view of moisture resistance, corona deterioration resistance and self recoverability.
In the method, the conventional work to adjust the evaporation condition of the auxiliary material in the evaporator in the auxiliary material evaporation step in reference to sensibility of the operator based on his or her experience is not substantially required, and the problem of fluctuation in the thickness of the deposited auxiliary material layer in the products obtained in one batch can be substantially solved.
In the production of a metallized film for a capacitor, the margin formation errors caused because of reliance on sensibility of the operator based on his or her experience can be eliminated and the poor adhesion between the films in the obtained capacitor can be overcome, to allow the production of a very good capacitor.
The auxiliary material may be an organic compound. The organic compound used is not too low in boiling point and is likely to be polymerized or crosslinked.
The auxiliary material may be an oil. Where the metal evaporated article is a metallized film for a capacitor, it is preferable to use a silicone oil or fluorine oil as the margin forming oil in view of electric properties. More preferable is a dimethyl polysiloxane, methyl phenyl silicone oil or perfluoropolyether, and further more preferable is methyl phenyl dimethyl polysiloxane oil or perfluoropolyoxyetane.
The auxiliary material may be water. It is preferable that the water is as pure as possible, containing few impurities.
An apparatus for producing a metal evaporated article, which is composed of (a) a metallization chamber, (b) a pressure reducing means for reducing the pressure in the metallization chamber, (c) substrate running means for running a substrate, (d) a metallization means and (e) an auxiliary material deposition means constituted by an evaporator for heating and evaporating an auxiliary material contained in it by a heating means, wherein in said metallization chamber, a metal is deposited by said metallization means onto the substrate run by said substrate running means, and before or after the metallization, the auxiliary material is deposited by said auxiliary material deposition means onto the substrate run by said substrate running means, comprising (f) a pressure detecting means for detecting the pressure in the atmosphere where the auxiliary material evaporated by said heating means of said evaporator exists, and (g) a temperature control means for controlling the heating temperature of said heating means based on the information concerning the detected pressure.
The evaporator has a heating means and contains an auxiliary material. The auxiliary material heated by the heating means is evaporated. The evaporated auxiliary material is discharged outside the evaporator from an opening of the evaporator. The discharged and evaporated auxiliary material is deposited onto the substrate.
The pressure of the atmosphere where the evaporated auxiliary material exists, i.e., the pressure reflecting the vapor pressure of the evaporated auxiliary material is detected by the pressure detecting means.
Based on the information concerning the detected pressure, the temperature of the heating means of the evaporator is controlled. This control keeps the deposition of the auxiliary material on the substrate substantially constant.
The detection end of the pressure detecting means may be placed in the atmosphere where the evaporated auxiliary material in the evaporator exists. A chamber pressure detecting means may be provided for detecting the pressure in the metallization chamber.
The metallization chamber may be kept in a reduced pressure atmosphere in the range of from about 1xc3x9710 Pa to about 1xc3x9710xe2x88x924 Pa, by the pressure reducing means for smooth metallization onto the substrate, and considering a case where the reduced pressure affects the detection of the pressure reflecting the vapor pressure of the auxiliary material, a chamber pressure detecting means for detecting the pressure in the metallization chamber is provided. With this, the influence of the pressure of the metallization chamber on the detection of the pressure of the atmosphere where the evaporated auxiliary material exists can be corrected.
A substrate speed detecting means for detecting the running speed of the substrate may be provided. A substrate speed detecting means for detecting the running speed of the substrate in the metallization chamber may be further provided. A case where the deposition quantity of the evaporated auxiliary material on the substrate varies depending on the running speed of the substrate is taken into account in this apparatus. This can solve the problem of relating the fluctuation in the running speed of the substrate to the variation in the quantity of the auxiliary material deposited on the substrate, while this adjustment can be little effected manually in reference to the sen sibility of the operator.